The invention resides in keyboards containing contact pads and contact foils and particularly such keyboards which are highly skid-, bend-, and twist-resistant.
In order to make the bottom structure of keyboards more bend and twist resistant, it is known to reinforce the bottom plate, which normally consists of injection molded plastic material, with reinforcement structures such as ribs or stiffening corrugations.
Moder keyboards as they are used, for example for personal computers have become very compact and lightweight because of the use of compact, highly efficient components.
In the past it has been practice to provide for each key a return spring and an involved return mechanism but today so-called key support mats of elastomeric material are used which, below the keys, have dome-shaped raised portions (so-called key domes) which are impressed upon actuation of a key in order to provide the required return force for the key. Furthermore, instead of the conductor plates used in keyboards in the past, the multilayer contact foil sets which include electrical contacts and conductors and which are used in today's keyboards, are much lighter.
The weight loss of such keyboards which comes with the use of such lightweight designs and materials is now such that it has become annoying to the keyboard operator since the keyboards often have only small support contact forces and consequently have a relatively small stability with respect to unintended skidding on their support surface. In addition, the lighter components result in a reduction of the bend and twist resistance of the whole keyboard.
In order to provide the keyboards with greater bend and twist resistance, it is known to reinforce the bottom plates, which generally consist of injection molded plastic material, with ribs or corrugations as disclosed, for example, in German patent application P 44 08 3319. This however leads to a housing geometry of substantially increased complexity which also requires complex injection molds which furthermore make it more difficult to remove the injection-molded parts from the molds.
It is further known to provide keyboards with legs which are mounted by means of beating structures disposed separately on the bottom plate of the keyboard.
It is the object of the present invention to provide a keyboard with a key support mat and a multi-layer contact foil set wherein, however the housing is simple in shape so that it can be easily injection molded but, by inclusion of the housing legs into the bottom plate the bend and twist resistance and also the stability of the keyboard is increased whereas assembly of the keyboard components remains simple.